Question

Question: Draw the structure corresponding to each common name:

a. α-methoxyvaleric acid

b. β-phenylpropionic acid

c. α,β-dimethylcaproic acid

d. α-chloro-β-methylbutyric acid

Short answer

Answer

a.

α-methoxyvaleric acid

b.

β-phenylpropionic acid

c.

α,β-dimethylcaproic acid

d.

α-chloro-β-methylbutyric acid

Step-by-step solution

Step-by-Step Solution Step 1: Common names of carboxylic acid

Most carboxylic acid compounds have a common name which is more widely used than its IUPAC name.

Common names are formed by using a common parent name with the suffix ‘-ic acid’.

For example, acetic acid found in vinegar is the common name for ethanoic acid.

Numbering carbon atoms in common names

The location of the substituent is designated in common names using Greek letters.

In this system, the carbon adjacent to the carboxyl carbon is the $\mathrm{\alpha }$ carbon. The $\mathrm{\beta }$carbon is the carbon adjacent to the$\mathrm{\alpha }$ carbon followed by the carbon. This is continued down the chain.

The last carbon in the chain is sometimes called the $\mathrm{\omega }$carbon.

Structure of given carboxylic acids

a. Valeric acid is the common name for pentanoic acid. Therefore, the compound is pentanoic acid with a methoxy group in the second position.

The structure is:

α-methoxyvaleric acid

b. Propionic acid is the common name for propanoic acid. Therefore, the compound is propanoic acid with a phenyl group in the third position.

The structure is:

β-phenylpropionic acid

c. Caproic acid is the common name for hexanoic acid. Therefore, the compound is hexanoic acid with methyl substituents at second and third positions.

The structure is:

α,β-dimethylcaproic acid

d. Butyric acid is the common name for butanoic acid. Therefore, the compound is butanoic acid with chloro and methyl substituents at second and third positions, respectively.

The structure is:

α-chloro-β-methylbutyric acid